1. Field of the Invention
The present invention relates generally to an apparatus for producing liners for manholes, drainage pipes, sewer pipes and the like.
2. Description of the Prior Art
Liners for manholes and other drainage or sewer system are known in the art. Typically, a liner is applied to a deteriorating manhole in order to rehabilitate the manhole and return it to a safe and working condition. Application of such liner systems requires that the surfaces of the existing structure be thoroughly cleaned prior to application of the liner material to insure a strong bond between the material and the underlying structure. It is also common to seal the surface of the existing structure with a watertight sealant prior to application of the liner material to prevent water and other foreign substances from leaking between the liner and the structure, thereby causing the liner to disbond and fail.
One such liner system is described in U.S. Pat. No. 5,618,616 (Hume). There a multilayered liner system is provided for rehabilitating waste water system components. The existing, deteriorated structure is thoroughly cleaned to allow proper bonding of the liner material. A first primer layer is applied to seal the surface and then a plurality of additional foam and barrier layers are applied, as required. Each layer is sprayed applied. This method is time consuming, expensive and can be dangerous, as the personnel applying the liner may be exposed to harmful chemicals in a closed space with little or no air flow.
Systems have been developed whereby an entire manhole assembly may be constructed prior to installation. Such systems are useful for replacing deteriorated or non-functional manholes in existing waste water system or for providing a chemical and corrosion resistant manhole for use in new waste water system construction. Such a system is described in U.S. Pat. No. 5,303,518 (Strickland). A plastic liner having a provisions for creating mechanical lock with an outer shell of concrete is provided wherein the a plurality of projections extend outwardly from the liner into the concrete outer shell. The concrete flows around and between the projections thereby mechanically locking the liner to the concrete. The projections are integral to the liner and therefore, the liner material must be a material capable of being molded or shaped to form such projections, for instance, polyethylene or polyvinylchloride (PVC). In certain cases, additional processing may be required to provide a completed liner. Such processing may include cutting or milling the exterior surface of the liner to provide sufficient gaps or spaces for concrete to bond to the liner.